A socket adapter for conventional light bulbs (incandescent light bulbs) have a larger external screw base, combined with an internal, smaller screw socket, so that a light bulb having a small screw socket is adapted to a large receiving socket (i.e., a lamp holder). Such a socket adaptor does not usually include any built-in power adapter because the conventional light bulb does not generally require any conversion of electric power.
Recently, an LED light bulb has been developed and has become popular as a replacement of an incandescent light bulb, because of its low power consumption and long life characteristic. An LED can be driven by AC or DC power. In an AC mode, the LED does not light up in a reverse cycle of the AC power. When the AC power is rectified, the LED can be lit up in a full-wave rectified alternating DC mode. For a DC mode, the AC power should be converted to DC power, and therefore an AC-DC converter that converts AC current to DC current is necessary.
There are two known methods for providing DC power to an LED lamp. One method is providing an AC-DC convertor (a DC power supply) in the LED lamp itself. In such a case, heat will build-up in the LED lamp due to the presence of both the DC power supply and the LED lamp, and cost of the LED lamp will increase. Further, it will be necessary to replace the entire LED lamp together with the AC-DC convertor if either one of the LED lamp or the AC-DC convertor fails.
Another method is providing an external AC-DC convertor (DC power supply), for example, in a wall switch or in a lighting fixture. This method avoids the heat build-up in the lamp. Since the increase in temperature in the LED lamp will reduce the efficiency of the LED, such as an external convertor may be desirable in terms of the efficiency of the LED lamp. The external AC-DC convertor, however, frequently requires a box for housing the convertor and a driver circuit, an AC power inlet and a DC output cable, which reduces flexibility of installment of the LED lamps. Having a separately attached AC-DC power convertor is also troublesome since it requires the end-user to install and hide the power supply somewhere away from the LED lamps. This involves additional installment cost.
An example of an external AC-DC convertor for LED lamps is found in U.S. Patent Application Publication No. 2010/0109558, the entirety of which is incorporated herein by reference.
Accordingly, there is a need for a compact and low cost AC-DC conversion system for an LED lamp as a replacement of an incandescent light bulb, which overcomes the foregoing problems.